1. Field of the Invention
The invention relates to a multi-position adjustable height seat post, specifically a tube within a tube that allows for the adjustment of seat height to multiple positions while riding a bicycle.
2. Description of the Prior Art
Cyclists, specifically those involved in mountain biking, find that it is beneficial to have a variety of seat height options while riding a bicycle. Seat height options are desired because they afford the rider greater control of the bicycle over widely varying terrain.
Riders descending steep or difficult terrain will benefit from a much lower seat height, thus allowing them to lower their center of gravity increasing their control over the bicycle. While riding on less difficult terrain a rider may want to only slightly lower their seat height for improved cornering, yet still maintain near full leg extension for good power transfer. Riding flat terrain or climbing the rider will want the seat at a ride height so as to obtain near full leg extension while remaining seated for optimal power transfer to the pedals.
Other seat posts have been proposed that allow the user to adjust the height of the seat to multiple positions while riding. The typical form exhibited by these seat posts is a tube within a tube with some form of locking mechanism. The outer tube mounts into a bicycle frame, while the inner tube inserts into the outer tube and carries a mount for the seat. The locking mechanisms come in many forms. There are two notable examples currently on the market. The first type, the Gravity Dropper seat post (U.S. Pat. No. 7,025,522 B2), uses a pin type mechanism wherein a pin from the outer tube is used to support the inner tube in multiple positions. The second type, the Speedball seat post by Maverick, is a pneumatically operated tube within a tube allowing infinite adjustability from 0 to 3 inches.
While both of these seat posts perform there intended duties we believe they have their shortcomings. In the case of the Gravity Dropper seat post a number of disadvantages are present:                (a) spring force acting on the inner tube exerts tremendous pressure on the locking pin causing it to become stuck in the inner tube, not allowing the inner tube to release from the outer tube. The rider has to place pressure on the inner tube opposite that of the spring force to release to pin from the inner post. This action creates unnecessary rider movement thus a loss of momentum and power transfer to the pedals.        (b) another issue associated with the Gravity Dropper is that the hole drilled in the inner tube to accept the locking pin of the locking mechanism creates a stress riser which can lead to a failure of the inner tube.        (c) another issue is manual adjustment of rotational and for-aft play with the use of a crimp nut. This adjustment requires the user to be mechanical inclined or requires the service of a mechanic at a local bicycle shop.In the case of the Speedball seat post a number of disadvantages are present:        (a) seat height adjustment and immobilization is obtained with the use of pneumatic force. Containing the pressure required to operate the pneumatics of the seat post requires the use of seals which may leak causing the failure of the locking mechanism.        (b) the seat post is also limited to larger diameter bicycle seat tubes of 30.9 mm or greater. This large diameter is greater than the most common size seat tube of 27.2 mm in diameter, therefore the Speedball is not available to most of the bicycle market.        (c) the seat post offer no means to adjust rotational or for-aft play as it becomes worn with use.        